The present disclosure relates to a safety mat for safeguarding a technical installation
As automation of production processes has increased, the requirements for reliable safety of industrial production installations have continuously increased. For example, revised EC Machinery Directive of 17 May 2006 describes a standard safety level for preventing accidents which is to be taken into consideration when a machine is placed on the market or put into service. Accordingly, technical installations, machines and robots may be commissioned only in conjunction with corresponding safety measures. These measures include, in particular, monitoring hazardous regions of a technical installation and moving the technical installation to a state which is safe for persons and objects in the event of (un)authorized access to the hazardous region.
So-called pressure or switching mats, as are described in DE 100 46 974 B4 for example, are known from the prior art for identifying the presence of persons. Safety mats of this kind are generally composed of two current-carrying plates which are separated from one another and which are held at a distance from one another by strip- or grid-like spacers. If a person steps on the safety mat, the plates and spacers deform until a cross-connection is formed between the plates. The cross-connection can be detected by measurement and causes a connected safety relay module to switch off the technical installation or to prevent the said technical installation from starting up. The general principles and requirements made in respect of design and testing of pressure-sensitive safety devices of this kind are defined in EN ISO 13856-1. In particular, the minimum safety requirements in respect of performance, marking and documentation are specified in the standard.
The abovementioned safety mats have the disadvantage that only a specific surface area section in front of a machine can be monitored and therefore safety mats can be used only in defined access regions or defined operator positions, while further access to the machine has to be prevented by other safety devices or structural measures. Particularly in the case of modern installations, such as robots which operate in an automated manner, are free-standing and have to be accessible from all sides for example, it is not possible to limit access to specific access regions. It is therefore desirable to be able to protect the entire region around the technical installation by a pressure-sensitive safety device which is arranged on the floor.
However, the safety mats mentioned in the introductory part cannot perform this either as individual safety mats or as a composite comprising several safety mats. The effective surface area of an individual safety mat is determined and therefore limited by the respective plate size. Similarly, for structural reasons, the sensitivity is not homogeneous over the surface area of the safety mat, as indicated in DE 10 46 974 B4, and therefore identification is only limited or not possible at all in the boundary regions in particular. In a composite, this results in large regions, in which reliable detection cannot be ensured, being formed at the transitions between the safety mats by boundary regions meeting one another.